KR20050058876A - Apparatus and method for controlling data rate of mobile terminal in a wireless communication system - Google Patents

Abstract

The present invention relates to an apparatus and a method for controlling a reverse rate in a mobile communication system.

The method according to the first embodiment of the present invention is a reverse data rate control method of a mobile terminal in a handoff state that communicates with one serving base station and one or more non-serving base stations in a mobile communication system. Receiving a power control command from the non-serving base station; and generating a random value within a preset range when the power control command received from the non-serving base station among the received power control commands indicates a decrease in the transmission rate, When the generated value is within a range capable of ignoring a preset rate reduction, ignoring the rate reduction and determining the rate according to the rate control command received from the serving base station.

Description

Apparatus and method for controlling data rate of mobile terminal in mobile communication system {APPARATUS AND METHOD FOR CONTROLLING DATA RATE OF MOBILE TERMINAL IN A WIRELESS COMMUNICATION SYSTEM}

The present invention relates to a rate control apparatus and method in a mobile communication system, and more particularly, to a reverse rate control apparatus and method of a mobile terminal.

In general, a mobile communication system providing a data service includes a packet data channel for transmitting packet data. When transmitting data in such a packet data channel, the data rate is determined by various factors such as the channel condition between the mobile terminal and the base station, the total system capacity, the amount of interference in the vicinity, the distance between the mobile terminal and the base station, and the amount of data to be transmitted. In addition, data transmission is generally classified into forward data transmission from the base station to the mobile terminal and reverse transmission from the mobile terminal to the base station. Therefore, the forward data rate refers to the transmission rate of the packet data channel transmitted from the base station to the mobile terminal, and the reverse data rate refers to the transmission rate of the packet data channel transmitted from the mobile terminal to the base station.

Now, a method of controlling the reverse data rate in the current synchronous code division multiple access (CDMA) mobile communication system will be described. When transmitting packet data in the reverse direction in the CDMA mobile communication system to date, the transmitted data is transmitted in units of physical layer packets (PLPs). The data rate of each physical layer packet is variable every packet, and in general, the determination of the data rate is performed by the base station. That is, the base station controls the transmission rate of various mobile terminals communicating with the base station. As such, the process of determining and controlling the data rate of the mobile station by the base station is called scheduling. The scheduling is performed by receiving information on the power of the mobile terminal, the amount of data to be transmitted by the mobile terminal, etc. from the corresponding mobile terminal and performing scheduling based on the information. Such scheduling is an operation performed by a scheduler of a base station. The scheduler of the base station is the 'Rise of Thermal (Rise of Thermal)' (hereinafter referred to as 'RoT') or the 'receive signal-to-noise ratio' of the mobile station belonging to the current base station (Base Transceiver Station (hereinafter referred to as "BTS") Scheduling is performed in consideration of the load obtained from '.

The method for controlling the reverse data rate of the mobile station by the base station according to the transmission method of the control information of the base station Dedicated Rate Control (hereinafter referred to as "DRC") and Common Rate Control (hereinafter referred to as "CRC") ""). The base station operating in DRC transmits different rate control information for each terminal belonging to the base station. On the other hand, the base station operating in CRC delivers common rate control information for all terminals in the base station. That is, since the base station operating in the DRC transmits control information to all terminals in the cell, the base station has a merit in that the transmission rate can be controlled more precisely than the CRC, and more control information needs to be transmitted.

Next, the case of operating as a CRC and a case of operating as a DRC will be described. First, the case of operating in the CRC mode will be described. The base station operating in the CRC mode transmits control information indicating that the uplink transmission state is 'Busy' for all terminals in the cell when the RoT value measured by the base station exceeds a predetermined limit value. On the other hand, if the RoT value measured by the base station does not reach the limit value, the base station transmits control information indicating that the uplink transmission state is 'Not Busy' for all terminals in the cell. Then, the terminal receiving the control information indicating the 'busy' state can lower the RoT level in the cell by lowering its data rate or the TPR described below, and the terminal receiving the control information indicating the 'Not Busy' state You can increase your data rate or TPR. Such 'Busy' and 'Not Busy' information can be transmitted through one bit of Rate Control Bit (RCB).

Next, the case of operating in the DRC mode will be described. The base station operating in the DRC mode controls the reverse data rate of the mobile terminal again according to the degree of transition of the reverse data rate of the terminal (Full Rate Transition) and Limited Rate Transition (Limited Rate Transition) It can be distinguished in a manner.

The full rate transition method is a method in which the base station does not limit the transition of the data rate in controlling the reverse data rate of the mobile terminal. The limited rate transition method is a method in which the base station limits the transition of the data rate in one step in controlling the reverse data rate of the mobile terminal.

For example, possible sets of data rates include 9.6 kbps, 19.2 kbps, 38.4 kbps, 76.8 kbps, 153.6 kbps, 307.2 kbps, and the like. Here, the number and specific values of data rates included in the data rate set may vary from system to system. In this case, in the full rate variation scheme, the base station determines all data rates in determining the data rate of the next packet for the mobile terminal. That is, the system allows the transmission rate of the terminal, which has been transmitted at 9.6 kbps, to be changed at 307.2 kbps at one time. The reverse rate of the terminal that the base station can tolerate is not limited by the previous transmission rate of the terminal. On the other hand, in the rate variation method, the base station limits the range of one step up or down from the previous packet rate in determining the data rate of the next packet of the terminal. For example, the rate control of the next packet of the base station for the terminal transmitting at 76.8 kbps is limited to one of 38.4 kbps, 76.8 kbps, 153.6 kbps. In other words, one step up, one step down, or maintenance is performed at the current data rate of 76.8kbps, which is a method of limiting the change of the data rate of the mobile terminal.

In the following, the operation of the base station and the mobile terminal in the rate limit transmission method, information transmission, and a channel for transmitting the information will be described.

When the scheduler of the base station can use the RoT, the RoT is scheduled to meet the 'reference RoT level', and when the RoT is not available, the load is scheduled to meet the 'Reference Load level'. The base station transmits data rate control information to the mobile terminal according to the scheduling result. Such data rate information is typically transmitted using a rate control bit (hereinafter referred to as "RCB"). The RCB is transmitted to a specific mobile terminal through a forward rate control channel (F-RCCH). As such, specific control information names or channel names used in this document are used for convenience of description. Therefore, it is obvious that other names can be used if the system is different. In a typical system, the RCB operates as follows. When the RCB value received from the base station is '+1' (up), the mobile station increases the data rate by one step in the next transmission interval, and decreases one step when the received RCB value is '-1' (down). In addition, if the received RCB value is '0' (hold), the data rate of the previous transmission interval is maintained.

1 is a signal flowchart in the case of controlling a reverse data rate in a mobile communication system using a limited rate transmission scheme.

In FIG. 1, the RCB is transmitted from the base station to the mobile terminal through a forward rate control channel (hereinafter, referred to as “F-RCCH”) 101. The RCB is used by the base station to control reverse rates of various mobile terminals. The reverse link of FIG. 1 is referred to as a reverse packet data control channel (hereinafter referred to as "R-PDCCH") 104 and a reverse packet data channel (hereinafter referred to as "R-PDCH"). 105), a reverse pilot channel (hereinafter referred to as "R-PICH") 106, and the like. The R-PDCCH is a control channel transmitted together with the R-PDCH and transmits a rate indication sequence (hereinafter referred to as "RIS") indicating a transmission rate of data transmitted on the R-PDCH. In the RIS, information such as a mobile status sequence (hereinafter, referred to as "MSS") of a mobile terminal that informs the power and buffer status of the mobile terminal is transmitted through this channel. Here, it should be noted that the type of information transmitted through the R-PDCCH and the number of bits thereof may vary depending on a specific system. Table 1 below shows the RIS field of the R-PDCCH and the R-PDCH data rate allocated thereto.

R-PDCCH RIS R-PDCH Data Rate 0000 0 kbps 0001 9.6 kbps 0010 19.2 kbps 0011 38.4 kbps 0100 76.8 kbps 0101 153.6 kbps 0110 307.2 kbps

As shown in Table 1, when the RIS field is '0001', it means that the R-PDCH is transmitted at 9.6 kbps. Other sequences are interpreted in the same way.

On the other hand, the MSS contains information on the state of the mobile terminal, the information is reported to the base station. In more detail, the mobile terminal considers the amount of data stored in its buffer and the power currently being transmitted by the mobile terminal, and whether the user wants to increase, maintain or decrease the data rate in the next transmission period. Create an MSS representing. Then, the generated MSS is transmitted to the base station and reported. It should be noted that the data transmission rate of the mobile terminal is not directly determined by the report, but should be approved by the scheduler of the base station again after the report. Detailed description thereof will be described later. Table 2 below shows an example of the MSS.

MSS meaning 00 MS requests an increase in bit rate 01 MS requests a reduced rate 10 MS requests to maintain bitrate 11 unused

As shown in Table 2, when the MSS is '00', it means that the mobile station requests to transmit data in the next transmission section at a data rate higher than the current section. If the MSS is '01', it means that the mobile station will lower the data rate by one step in the next transmission section than in the current section. It should be noted that, unlike the case of increasing the transmission rate, the mobile terminal does not make a request but notifies a request. This is because lowering the data rate does not adversely affect the system even if it is done without the permission of the base station. On the other hand, when the MSS is '10', it means that the MS requests the same data rate as in the current section even in the next transmission section. The case where the MSS is '11' is not yet defined, and may be used later.

Now, a method of operating a rate control of a mobile terminal in the prior art will be described in detail with reference to the example of FIG. 1. At 107, the data to be transmitted to the base station arrives in the buffer of the mobile terminal. That is, data to be transmitted is generated at the request of a specific application or user. When the data to be transmitted is generated as described above, the mobile terminal starts to transmit the data in the buffer at the reference data rate 108 at the minimum data rate of 9.6 kbps. Here, it is assumed that the system of FIG. 1 allows all mobile terminals to transmit a minimum data rate of 9.6kbps without control of the base station. In addition, it is assumed that the transmission power of the mobile terminal at time 108 is sufficiently smaller than the maximum transmission power limit value of the mobile terminal.

The mobile station transmits 9.6 kbps of data through the R-PDCH at time 108 and simultaneously transmits the above-described RIS and MSS through the R-PDCCH. Since the data rate of the R-PDCH is 9.6kbps, the RIS becomes '0001' as shown in the example of Table 1 above. In addition, the MSS becomes '00' because the mobile terminal can transmit data higher than 9.6kbps.

The base station receives the R-PDCH and the R-PDCCH transmitted for one frame at time 108 and performs scheduling based on the received information. That is, by analyzing the MSS '00' received from the mobile terminal, it is determined that the mobile terminal wants to increase the data rate, and the sum of the reverse received signals from the other mobile terminals or the total RoT or reverse full load, etc. In consideration of this, it is determined whether the data rate of the mobile terminal can be increased.

In FIG. 1, it is assumed that the base station determines that the mobile station increases the data rate as a result of the scheduling. Therefore, the base station generates the RCB according to the scheduling result. Therefore, the base station transmits the RCB to increase the data rate to the mobile terminal through the F-RCCH at 102. The mobile terminal raises the data rate by one step with reference to the transmitted RCB at reference numeral 109. As shown in Table 1, data is transmitted at 19.2kbps, which is one step higher than 9.6kbps. At this time, the RIS of the R-PDCCH transmitted together with the R-PDCH at reference numeral 109 becomes '0010'.

The base station and the mobile station repeat the above-described process until the mobile station transmits all the data in the buffer. According to the above process, the mobile station can gradually increase the data rate step by step based on the amount of data in the mobile station's buffer, the current transmit power relative to the mobile station's maximum power limit, and the uplink overall resource distribution of the base station. If the mobile terminal transmits all data, the mobile terminal stops transmitting data. If data transmission of the mobile station is stopped, the R-PDCCH transmits information of the RIS '0000'.

In the above-described conventional technology, the mobile terminal receives power control bits transmitted from the base station and interprets them as shown in Table 3 below.

Rate control bits meaning +1  One step up rate is allowed. 0  It is allowed to keep the transfer rate at the current level. -One  Lower bit rate by one step.

On the other hand, when the mobile terminal is performing a soft handoff, the mobile terminal receives the rate control bits from several base stations. That is, the mobile terminal receives rate control bits from several base stations performing soft handoff and determines the final rate control bits according to a predetermined rule. In a typical mobile communication system, when a mobile terminal is performing a soft handoff, one primary base station among multiple base stations performing a soft handoff is called a serving base station, and other non-serving base stations are called. It is called a (non-serving) base station. In addition, in a typical system, the serving base station may transmit an up, down, and hold command as a rate control bit to the mobile terminal performing the handoff. On the other hand, non-serving base stations limit the transmission of only down commands. Therefore, when the mobile terminal performing the handoff receives the rate control bits from several base stations, the rate control bits received from the serving base station are interpreted as one of +1 (up), 0 (hold), and -1 (down). The rate control bit received from the non-serving base station determines whether or not -1 (down). In other words, when it is not determined that -1 is received from the non-serving base station, it is determined that the rate control bit has not been received from the non-serving base station. As described above, in the general mobile communication system, the reason why the non-serving base station can transmit only a down command to the mobile terminal is to limit the non-serving base station from actively participating in the rate control of the mobile terminal. . In addition, the reason for allowing the down command is to reduce the transmission rate of the mobile stations when the non-serving base station is in an over-loaded situation.

In addition, the method of transmitting a rate control bit to a mobile station by a base station in the limited rate transmission system includes a method of transmitting a dedicated command for each mobile terminal. The method of transmitting a dedicated command in the above means allocating a physical or logical channel for only one mobile terminal. For example, if there are two mobile terminals in the system, the base station refers to a method of separately assigning the F-RCCH to which the rate control bits are transmitted to the two mobile terminals. Accordingly, in the method of transmitting the dedicated command, the F-RCCHs received by the mobile station A and the mobile station B are different channels.

However, in a conventional dedicated rate control system, a base station allows rate control through a single F-RCCH for several mobile terminals having themselves as non-serving base stations. For example, suppose that there is a base station A, and there are mobile terminals a, b, and c performing handoff, the mobile terminal a has a base station B as a serving base station and a base station A as a non-serving base station. Further, assume that mobile terminals b and c have base station C as the serving base station and base station A as the non-serving base station. In the above example, since the mobile stations a, b, and c all use the base station A as the non-serving base station, the base station A may only give a down command to the mobile terminals a, b, and c. In the above example, the base station A may allocate a common F-RCCH to the mobile stations a, b, c. In other words, the mobile stations a, b, and c receive the same rate control bits from the base station A on the same F-RCCH. As described above, the base station transmits a common rate control bit to one or more mobile stations through a single F-RCCH. This scheme is called a common rate control scheme. The base station A allocates dedicated F-RCCHs to the mobile stations a, b, and c, and also assigns common F-RCCHs to the mobile stations a, b, and c. Mobile terminals a, b, and c receive rate control bits from the base station A on the commonly assigned F-RCCH while base station A is a non-serving base station. However, when the base station A changes to a serving base station, the base station A receives a rate control bit through a dedicated F-RCCH.

A limited rate transmission mobile communication system using a combination of the dedicated rate control method and the common rate control method described above may have the following problems. There are mobile terminals a, b, c, d, and e having base station A as a non-serving base station, and the base station A allocates a common F-RCCH to the mobile terminals of a, b, c, d, and e. Suppose you are sending a common rate control bit. Assume that the mobile terminal a is transmitting packet data at 307.2 kbps and the mobile terminals b, c, d, and e are transmitting packet data at 76.8 kbps at any point in time. In addition, at any point in time, base station A assumes a situation in which a downlink load command is greater than a specific threshold to give the mobile station a rate-down command.

Under the above assumption, when the base station A transmits a down command through a common F-RCCH, the mobile stations of a, b, c, d, and e must all decrease the data rate by one step. Accordingly, the data rates of the mobile terminals of a, b, c, d, and e having received the common rate control bit 'down' will be decreased by one step, and thus will be 153.6, 38.4, 38.4, 38.4, and 38.4 kbps, respectively. As described above, when the reverse load exceeds the specific threshold, the base station A lowers the data rate by one step to all other mobile terminals even if the situation can be solved by lowering the data rate of the mobile station a from 307.2kbps to 153.6kbps. In other words, according to the presently proposed scheme, when the reverse load exceeds a threshold, the base station cannot selectively control the mobile station's transmission rate and lower the data rate more than necessary, thereby reducing the throughput. There is a problem that can degrade performance.

Accordingly, an object of the present invention is to provide an apparatus and method for efficiently controlling reverse data rate in a mobile communication system.

Another object of the present invention is to provide an apparatus and method for increasing overall efficiency in controlling reverse data rates in a mobile communication system using a limited rate transmission scheme.

It is still another object of the present invention to provide an apparatus and method for controlling a data rate to increase the overall transmission efficiency according to the data rate of each mobile terminal when controlling a reverse data rate in a mobile communication system using a limited rate transmission scheme. .

The apparatus according to the first embodiment of the present invention for achieving the above objects, the reverse data rate control of the mobile terminal in the handoff state to communicate with one serving base station and one or more non-serving base station in the mobile communication system An apparatus, comprising: a receiver for receiving a power control command from the serving base station and the non-serving base station, and determining and outputting a received power control command; and a power control command received from a non-serving base station among power control commands output from the receiver. A rate received from the serving base station, ignoring the rate reduction, when generating a random value within a preset range when instructing this rate reduction, and when the generated value is within a range capable of ignoring a preset rate reduction; A control unit for determining a transmission rate according to a control command; And a transmitter for transmitting packet data in the reverse direction according to the transmission rate determined by the controller.

The method according to the first embodiment of the present invention for achieving the above object, the reverse data rate control of the mobile terminal in the handoff state to communicate with one serving base station and one or more non-serving base station in the mobile communication system A method, comprising: receiving a power control command from the serving base station and the non-serving base station, and if the power control command received from a non-serving base station among the received power control commands indicates a rate reduction, Generating a value of, ignoring the rate reduction and determining the rate according to a rate control command received from the serving base station when the generated value is within a range capable of ignoring a preset rate reduction. .

An apparatus according to a second embodiment of the present invention for achieving the above object, the reverse data rate control of a mobile terminal in a handoff state to communicate with one serving base station and one or more non-serving base station in a mobile communication system An apparatus, comprising: a receiver for receiving a power control command from the serving base station and the non-serving base station, and determining and outputting a received power control command; and a power control command received from a non-serving base station among power control commands output from the receiver. A control unit for ignoring the data rate reduction and determining a data rate according to a data rate control command received from the serving base station when the current data rate is not greater than a preset data rate when the data rate is instructed, and a reverse direction according to the data rate determined by the control unit. To send packet data via Contains the bride.

A method according to a second embodiment of the present invention for achieving the above object, the reverse data rate control of a mobile terminal in a handoff state performing communication with one serving base station and one or more non-serving base station in a mobile communication system The method may further include receiving a power control command from the serving base station and the non-serving base station, and when a power control command received from a non-serving base station among the received power control commands indicates a decrease in data rate, the current rate is preset. Checking whether the transmission rate is greater than the transmission rate, and if the transmission rate is not greater than a preset transmission rate, ignoring the reduction of the transmission rate, and determining the transmission rate according to the transmission rate control command received from the serving base station.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. First of all, in adding reference numerals to the components of each drawing, it should be noted that the same reference numerals have the same reference numerals as much as possible even if displayed on different drawings. Terms to be described later are terms defined in consideration of functions in the present invention, and may be changed according to intentions or customs of users or operators. Therefore, the definition should be made based on the contents throughout the specification.

The present invention describes operations performed in a limited rate transition mobile communication system using a combination of a dedicated rate control scheme and a common rate control scheme. In the mobile communication system according to the present invention, when a non-serving base station transmits a 'down' command as a common rate control bit, several mobile terminals having the base station as the non-serving base station receive the same. In controlling the data rate, a method will be described in which not all mobile terminals all reduce the transmission rate, but only some mobile terminals reduce the transmission rate by a method described below. In the implementation of the above-described proposal, it should be noted that not only the embodiments described in the present invention but also various modified methods may exist. This method will be described by two embodiments.

The first embodiment is a method in which a mobile terminal performs a self probability test. A detailed method of performing the self probability test will be described with reference to FIG. 4 below. The second embodiment is a method in which only a mobile terminal transmitting data at a higher transmission rate than a specific transmission rate lowers the data transmission rate. As described above, a detailed method of reducing a transmission rate for a terminal having a specific transmission rate or more will be described with reference to FIG. 5.

2 is a block diagram of a mobile terminal according to an exemplary embodiment of the present invention. Hereinafter, a block configuration and an operation according to each configuration of a mobile terminal according to an exemplary embodiment of the present invention will be described in detail. In addition, it should be noted that FIG. 2 illustrates only a configuration necessary for describing the present invention.

The mobile terminal mentioned in the present invention is a mobile terminal present in a handoff situation. In addition, the mobile communication system according to the present invention uses a dedicated rate control scheme and a common rate control scheme in the forward direction. Therefore, since the mobile terminal is in a handoff situation, the serving base station receives a command to increase, maintain, or decrease the transmission rate through a dedicated F-RCCH. A command to reduce the transmission rate is received from the non-serving base station through the common F-RCCH. Accordingly, in FIG. 2, the receiver 210 receives the RCB through the dedicated F-RCCH and simultaneously receives the RCB through the common F-RCCH. The power control message received through the dedicated F-RCCH and the common F-RCCH is received by the receiver 210 to determine despreading, symbol defects, and rate control bits, and are input to the controller 211. Detailed configuration of the receiver 210 will be described in more detail with reference to FIG. 3.

When the transmission rate control bit determined as described above is input, the control unit 211 determines a transmission rate to be transmitted in the reverse direction by the control process of FIG. 4 or FIG. 5 to be described later. The rate control process performed by the control unit 211 will be described in more detail later with reference to FIGS. 4 and 5. In addition, the controller 211 generates a message for reporting the state information of the mobile terminal to the base station by using the amount of data stored in the transmission memory 212 and the remaining power that can be transmitted in the reverse direction. The message generated as described above is output to the transmitter 213 to transmit through the R-PDCCH as shown in FIG. The controller 211 controls transmission of the R-RICH and controls the R-PDCH.

The transmission memory 212 is a memory that stores data to be transmitted in the reverse direction. The transmission memory 212 reports to the control unit 211 information on the amount of data to be transmitted in the reverse direction, and outputs the data corresponding to the amount to be transmitted to the transmission unit 213 under the control of the control unit 211. The transmitter 213 continuously transmits the R-PICH under the control of the controller 211, encodes and modulates the data output from the transmission memory 212, configures it into packets, and transmits the same through the R-PDCH. In addition, the transmitter 213 configures a control message in consideration of the state of the buffer and the state of the mobile terminal output from the controller 211 and transmits the same through the R-PDCCH.

3 is a block diagram of an F-RCCH receiver of a mobile terminal according to an embodiment of the present invention. That is, FIG. 3 illustrates only a configuration for receiving the F-RCCH among the configurations of the receiver 210 of FIG. 2 described above. In FIG. 3, a configuration in which a signal received through a dedicated / common F-RCCH received through a wireless channel is band-down converted and converted into a baseband signal is not shown. Therefore, in FIG. 3, the signal received by the dedicated / common F-RCCH becomes a baseband signal. The baseband signal is despread in despreader 302. At this time, the despreader 302 despreads each signal received through the dedicated / common F-RCCH. The despread signal is thus input to the symbol summer 303. The symbol adder 303 receives the despread signal, divides each signal, and sums and outputs the symbols according to a predetermined number of repetitions. The symbol sum signal is thus determined by the rate control bit determiner 304 and outputs the rate control bit. That is, a signal received on a dedicated F-RCCH channel will indicate one value of increase / decrease / maintenance, and a signal received on a common F-RCCH channel will indicate one of decrease / ignore. The information output in this way is output to the controller 211.

4 and 5, a control process for reverse rate control in a mobile terminal in a handoff situation according to an exemplary embodiment of the present invention will be described.

4 is a flowchart illustrating a reverse rate transmission and a reverse data transmission in a mobile terminal in a handoff situation according to the first embodiment of the present invention. Hereinafter, a process of determining a reverse data rate and a control process of reverse data transmission according to the first embodiment of the present invention in a mobile terminal in a handoff situation will be described in detail with reference to FIGS. 2 to 4. In particular, FIG. 4 will be described with an emphasis on a process of determining a data rate of a mobile terminal performing a handoff after receiving a common rate control bit from a non-serving base station through a commonly allocated F-RCCH. .

If data to be transmitted in the reverse direction is generated, the mobile station performs reverse packet transmission in step 400. This process may be the time point 108 of FIG. 1 or the time point thereafter. When the mobile station transmits the packet in the reverse direction as described above, the base station transmits a rate control bit on the F-RCCH as described in the prior art. Therefore, the mobile station receives the reverse rate control bits. In FIG. 4, since the process is performed in the handoff situation, both the common F-RCCH from the non-serving base station and the dedicated F-RCCH from the serving base station are received. The mobile station proceeds to step 402 after transmitting the packet in the reverse direction in step 400 and receives the common rate control bit from the F-RCCH, the receiver of FIGS. 2 and 3 analyzes it. This is a process in which not only the common rate control bit but also the dedicated rate control bit are performed. In FIG. 4, since a control flowchart is constructed based on the contents of the present invention, it is assumed that only a common rate control bit is received. This common rate control bit is also received by the number of non-serving base stations participating in the handoff. Therefore, it should be noted that not only one rate control bit is received.

When the controller 211 receives the rate control bit, the controller 211 proceeds to step 404 to check whether the common rate control bit determined by the receiver 210 indicates a decrease in the rate. If the common rate control bit does not indicate a decrease in the rate as a result of the check in step 402, the operation proceeds to step 406.

First, a case in which the rate control bit does not indicate a rate reduction will be described. The case where the rate control bit does not indicate a rate reduction is a case where all base stations participating in the handoff do not indicate a rate reduction. That is, if even one base station instructs to decrease the transmission rate, the process proceeds to step 410. Therefore, the controller 211 ignores the rate control bits received from the non-serving base stations in step 406. In step 408, the transmission rate of the packet to be transmitted in the reverse direction is determined according to the transmission rate control bit received from the serving base station. In operation 420, the reverse packet is transmitted at the determined transmission rate.

On the other hand, the process from step 404 to step 410 is a case in which any one of the non-serving base station participating in the handoff of the mobile terminal in the handoff situation instructed to reduce the transmission rate. In this case, the controller 211 proceeds to step 410 to generate a random number. This random number means generating a random number within a predetermined range. The controller 211 generating the random number as described above proceeds to step 412 and compares the threshold value provided in advance with the size of the generated random number. As a result of the comparison of the magnitudes, if the random number is larger than the threshold value provided in advance, the process proceeds to step 414; otherwise, the process proceeds to step 406 described above. Here, the threshold value may be set in advance between the base station and the terminal and may be determined during product design of the mobile terminal. If the value is predetermined between the mobile terminal and the base station, it is received from the base station in a predetermined memory (not shown in FIG. 2) when the first mobile terminal is powered on or proceeds to a handoff situation. Can be stored and used.

In the above, when the transmission rate control bits received from all non-serving base stations indicate a decrease, a case in which a test for reducing the transmission rate is performed only once, that is, steps 410 and 412 are described. However, other methods can be used. Alternatively, if there is more than one non-serving base station and a value indicating the rate control bit is received from two or more non-serving base stations, steps 410 and 412 may be performed as many as the number of non-serving base stations indicating a rate reduction. Perform iteratively. Performing the above operation has the following advantages.

The fact that the other base stations have a large value indicating the rate reduction means that the reverse load of the non-serving base stations is large. Therefore, non-serving base stations may be more desirable to reduce the transmission rate by one step even in a mobile terminal having a relatively low transmission rate. Therefore, in this case, the mobile station performs a check for reducing the transmission rate received from the non-serving base station by increasing the number of times the reduction rate is indicated, thereby increasing the probability of reducing the transmission rate. In this way, the improvement can be seen in terms of overall efficiency of the system.

When the controller 211 proceeds from step 412 to step 414, the controller 211 determines the reverse packet rate at a data rate lower than the current data rate. This step becomes a data rate lower than one of the rate levels as shown in Table 1 described in the prior art. For example, if the transmission rate of the current mobile terminal is 38.4kbps, the next lower rate level is 19.2kbps. When the data rate is determined as described above, the controller 211 proceeds to step 420 to transmit the reverse packet. However, if the current data rate of the mobile terminal is the lowest data rate, that is, 9.6 kbps of Table 1, the data rate cannot be lowered. Thus, two such cases would be possible. One way is to ignore the received data rate reduction command. Another way is to stop reverse data transmission. However, it is preferable to ignore the data rate reduction command in such a case, rather than to interrupt the reverse data transmission, in view of guaranteeing the quality of service.

5 is a flowchart illustrating a reverse rate transmission and a reverse data transmission in a mobile terminal in a handoff state according to the second embodiment of the present invention. Hereinafter, a process of determining a reverse data rate and a control process of reverse data transmission in a mobile terminal in a handoff situation according to the second embodiment of the present invention will be described in detail with reference to FIGS. 2, 3, and 5. In particular, FIG. 5 will be described with an emphasis on a process of determining a data rate of a mobile terminal performing a handoff after receiving a common rate control bit from a non-serving base station through a commonly allocated F-RCCH. .

If data to be transmitted in the reverse direction is generated, the mobile station performs reverse packet transmission in step 500. This process may be the time point 108 of FIG. 1 or the time point thereafter. When the mobile station transmits the packet in the reverse direction as described above, the base station transmits a rate control bit on the F-RCCH as described in the prior art. Therefore, the mobile station receives the reverse rate control bits. In FIG. 5, since the process is performed in the handoff situation, both the common F-RCCH from the non-serving base station and the dedicated F-RCCH from the serving base station are received. The mobile station proceeds to step 502 after transmitting the packet in the reverse direction in step 500 and receives the common rate control bit from the F-RCCH, the receiver of FIGS. 2 and 3 analyzes it. This is a process in which not only the common rate control bit but also the dedicated rate control bit are performed. In FIG. 5, since a control flowchart is constructed based on the contents of the present invention, it is assumed that only a common rate control bit is received. This common rate control bit is also received by the number of non-serving base stations participating in the handoff. Therefore, it should be noted that not only one rate control bit is received.

When the controller 211 receives the rate control bit, the controller 211 proceeds to step 504 to check whether the common rate control bit determined by the receiver 210 indicates a decrease in the rate. In step 502, if the common rate control bit does not indicate a decrease in the rate, the operation proceeds to step 506. If the common rate control bit does not indicate a decrease in the rate, the flow proceeds to step 510.

First, a case in which the rate control bit does not indicate a rate reduction will be described. The case where the rate control bit does not indicate a rate reduction is a case where all base stations participating in the handoff do not indicate a rate reduction. That is, if even one base station instructs to reduce the transmission rate, the process proceeds to step 510. Therefore, the controller 211 ignores the rate control bits received from the non-serving base stations in step 506. In operation 508, the transmission rate of the packet to be transmitted in the reverse direction is determined according to the transmission rate control bit received from the serving base station. In operation 520, the reverse packet is transmitted at the determined transmission rate.

On the other hand, the process from step 504 to step 510 is a case where any one of the non-serving base stations participating in the handoff of the mobile terminal in the handoff situation instructed to reduce the transmission rate. In this case, the controller 211 proceeds to step 510 to compare the current transmission rate with a predetermined threshold value. As a result of the comparison of step 510, if the current transmission rate is greater than the predetermined threshold value, the process proceeds to step 512. If the current transmission rate is smaller than the predetermined threshold value, the following process of step 506 is performed. Here, the threshold value may be set in advance between the base station and the terminal and may be determined during product design of the mobile terminal. If the value is predetermined between the mobile terminal and the base station, it is received from the base station in a predetermined memory (not shown in FIG. 2) when the first mobile terminal is powered on or proceeds to a handoff situation. Can be stored and used.

If the current transmission rate is greater than the predetermined threshold as a result of the check in step 510, the mobile terminal proceeds to step 512 and determines to lower the data rate by one step. This step becomes a data rate lower than one of the rate levels as shown in Table 1 described in the prior art. For example, if the current mobile terminal has a data rate of 307.2 kbps, the next lower data rate is 153.6 kbps. When the data rate is determined as described above, the controller 211 proceeds to step 520 to transmit the reverse packet.

As described above, in the second embodiment, a mobile terminal having a low data rate has an advantage of performing backward transmission without a significant burden by not decreasing the reverse data rate even when the reverse data rate indicates a decrease.

As described above, when the mobile terminal in the handoff situation determines the reverse data rate, all the mobile terminals unconditionally decrease the data rate without decreasing the data rate unconditionally, thereby reducing the throughput of the entire system. ) Has the advantage of increasing. In addition, the mobile stations that do not reduce the transmission rate have the advantage of improving the quality of service by performing the reverse transmission smoothly.

1 is a signal flow diagram when a reverse data rate is controlled in a mobile communication system using a limited rate transmission scheme;

2 is a block diagram of a mobile terminal according to an embodiment of the present invention;

3 is a block diagram of an F-RCCH receiver of a mobile terminal according to an embodiment of the present invention;

4 is a flowchart illustrating a reverse rate transmission and a reverse data transmission in a mobile terminal in a handoff situation according to the first embodiment of the present invention;

5 is a flowchart illustrating a reverse rate determination and reverse data transmission in a mobile terminal in a handoff situation according to another embodiment of the present invention.

Claims (4)

An apparatus for controlling a reverse data rate of a mobile terminal in a handoff state for communicating with one serving base station and one or more non-serving base stations in a mobile communication system, A receiving unit which receives a power control command from the serving base station and the non-serving base station and determines and outputs the received power control command; When the power control command received from the non-serving base station among the power control commands output from the receiver indicates a rate reduction, an arbitrary value within a preset range may be generated, and the generated value may ignore the preset rate reduction. A control unit for ignoring the rate reduction when present within a range and determining a rate according to a rate control command received from the serving base station; And a transmitter for transmitting packet data in a reverse direction according to the transmission rate determined by the controller. A method of controlling reverse data rate of a mobile terminal in a handoff state in which a mobile communication system communicates with one serving base station and one or more non-serving base stations, Receiving a power control command from the serving base station and the non-serving base station; If a power control command received from a non-serving base station among the received power control commands indicates a rate reduction, a random value is generated within a preset range, and the generated value is within a range that can ignore the preset rate reduction. When present, ignoring the rate reduction and determining a rate according to a rate control command received from the serving base station. An apparatus for controlling a reverse data rate of a mobile terminal in a handoff state for communicating with one serving base station and one or more non-serving base stations in a mobile communication system, A receiving unit which receives a power control command from the serving base station and the non-serving base station and determines and outputs the received power control command; If a power control command received from a non-serving base station among the power control commands output from the receiver indicates a decrease in transmission rate, the transmission rate is ignored and the transmission rate received from the serving base station is ignored when the current transmission rate is not greater than a preset transmission rate. A control unit for determining a transmission rate according to a control command, And a transmitter for transmitting packet data in a reverse direction according to the transmission rate determined by the controller. A method of controlling reverse data rate of a mobile terminal in a handoff state in which a mobile communication system communicates with one serving base station and one or more non-serving base stations, Receiving a power control command from the serving base station and the non-serving base station; Checking whether a current transmission rate is greater than a preset transmission rate when the power control command received from the non-serving base station indicates a reduction in the received power control commands; And determining the transmission rate according to the transmission rate control command received from the serving base station, ignoring the reduction of the transmission rate if the transmission rate is not greater than a preset transmission rate.